I've never had a problem with this machine until last week.
During the spin cycle it is much louder and it sounds like the load is off balance..........it isn't.
I found the drain tub plugged with what looks like concrete particles/flakes. I removed about a half-cup of the stuff. I put a nylon sock on the drain tube, secured it with a nylon tie, and ran another load. The "stuff" put a hole in the sock and I found more of the same particles in the drain tub. I used a different detergent last week but it is another liquid. The "stuff" doesn't appear in any other sinks in this house.